Current take-off brush assembly



Mar 1955 J. E. DIEHL ETAL CURRENT TAKE-OFF BRUSH ASSEMBLY Filed Nov. 29, 1962 a w m m WMFR 1a. VE/K afia Ewe 0 IE Nw wow w w G M A TTORNE K5.

3,173,046 Patented Mar. 9, 196.5

3,173,046 CURRENT TAKE-OFF BRUSH ASSEMBLY John 'E. Diehl, Edwin F. Klefer, and Walter G. Krellner,

St. Marys, Pa., assignors to Stackpole Carlson Company, St. Marys, Pa, a corporation of Pennsylvania Filed Nov. 29, 1962, Ser. No. 240,935

6 Claims. (Cl. 310-246) This invention relates to electric brushes, and more particularly to a brush formed from a pair of thin carbon brush half-sections disposed face to face.

It is common practice to make an electric brush for a rotating electrical machine from two similar half-sections that are disposed face to face. The two sections are thin, by which is meant that their thickness is so small in relation to their length that when they are used with reversible commutators or slip rings they tend to tilt in the brush holder in a clockwise or counter-clockwise direction, depending upon the direction of rotation of the electrical collector against which they ride. Any such change in the position of the brush halves, particularly upon and immediately after reversing the direction of rotation of the machine, results in new line contacts with the collector surface and eventually in so called double seating. Even though the brushes do not get into a chattering condition because of the slight leading angle allowed by the necessary clearance in the brush holder, and do not chip or break before the second seat is formed, the new location of electrical contact results in a different and less favorable time of commutation for each direction of rotation, whereby performance of the machine and the life of the brushes and commutator are impaired.

To avoid such unsatisfactory conditions it has been recognized that it i desirable to continually maintain both sides of the brush in contact with the opposite sides of the brush holder passage in which the brush is mounted. One way of doing this has been to provide the outer ends of the brush sections with inwardly beveled surfaces, against which pressure is applied to urge the sections apart and into engagement with the opposite sides of the brush holder. Such a system has value but, since all of the pressure is applied only to the outer end of the brush, there is little or no lateral pressure to spread the inner ends of the brush sections apart.

It is an object of this invention to provide an electric brush of the split or two section type, which always engages substantially fiat against opposite sides of the brush holder passage, regardless of the direction of rotation of the electrical machine with which the brush is used. Another object is to do this in a simple and inexpensive manner that does not require the brush holder to be modified and that does not reduce the allowable wear of the brush.

In accordance with this invention a resilient member is disposed between the inner faces of a pair of thin carbon brush half-sections. The resilient member engages both faces and is connected to one of the sections. This member preferably is mounted in a recess in one of the sections about midway between the ends of the brush. The resilient member can be compressed when the two sections are squeezed toward each other in order to permit the assembly to be inserted in a brush holder passage. When the brush then is released, the expanding resilient member spreads the two sections apart and holds them against the opposite sides of the passage. Their engagement with those sides continues, regardless of the direction of rotation of the commutator or slip ring engaged by the brush.

The invention is illustrated in the accompanying drawings, in which PEG. 1 is a view of one end of a brush holder containing our brush;

FIG. 2 is a cross section taken on the line II-II of PEG. 1; and

FIG. 3 is a view, similar to FIG. 1, of a modification, with parts of the holder and one of the brush sections broken away.

Referring to FIGS 1 and 2 of the drawings, a brush holder ll of suitable well-known construction is mounted beside a rotating cylindrical electrical collector 2, such as the commutator or slip ring of a rotating electrical machine (not shown). For convenience of description only, the rotating collector will be referred to herein as a commutator. The machine is reversible, so that the commutator can be rotated in either direction. The brush holder is provided with a rectangular passage 3 that is disposed radially of the commutator and a short distance away from it. Mounted in an opening in the holder outside of the brush passage is a spiral spring 4, the outer end of which carries a pad 5 for pressing against a brush B slidably mounted in the passage. The spring holds the inner end of the brush against the commutator at all times. As is common practice, the brush is formed from a pair of thin carbon half-sections 7 and 8 that are disposed face to face, with their opposed inner faces substantially parallel. Their outer ends, engaged by the spring pad, pr f rably are rounded and are connected in the usual manner by shunt wires 9 to a common terminal (not shown) It is a feature of this invention that regardless oi the direction in which the commutator is rotated, both sections of the brush will continually engage the brush holder flat against the adjoining opposite sides of; passage}. Accordingly, resilient means is compressed between the inner faces of the two brush sections inside the brush holder and forces the half-sections apart far enough to hold their outer faces against the sides of the brush holder passage. At least part of the resilient means is located about midway between the opposite ends of the brush so that it will exert pressure against the central portions of the half-sections, and it may take the form of two laterally spaced members 11. Even better results are obtained. it two more such resilient members 12 are disposed between the brush sections near their outer ends.

Each resilient member may be formed in any suitable manner, such as from a wire spring or, as shown, from a rubber-like plug. Each plug 'is connectedto only one of the brush sections so that it will not interfere with longitudinal movement or" the section relative to each other. Preferably, the resilient plugs are mounted in recesses or sockets 13 formed in the inner face of one brush section. The plugs can be glued or otherwise fas tened in the sockets. Of course the plugs project from the sockets so that they can exert pressure against the other half of the brush.

In order to insert the brush in the brush holder, the two halves of the brush have to be squeezed together slightly by ones fingers to compress the resilient plugs. With the outer end of spring 4 held out of the way, the brush then is inserted in the outer end of the holder passage and released, whereupon the plugs will expand and press the outer faces of the brush against the adjoining opposite sides of the passage. The brush is pushed down into engagement with the commutator and the spring pad 5 is seated on the outer end of the brush as shown in FIG. 2. It will be seen that with this construction neither section of the brush will be tilted in the brush holder while the commutator is rotating, regardless of its direction of rotation, because the resilient plugs will hold the sections parallel and against the holder. As a result, chatter, chipping and breakage are avoided, the brush seat is not changed with reversal of the commutator, the life of the brush and commutator are increased, and performance of the machine remains good. Each brush half is subjected to the desired individual damping action song the entire length of the adjoining brush holder surface, due to the friction between the engaging brush and holder surfaces as well as that between the resilient members and the brush half against which they are free to slide. On commutating machines, another important advantage results from the mechanical damping and separation afforded both brush halves in the case of resilient members having high electrical resistivity or those having high electrical contact resistance with either or both brush halves. Considered as a whole, the brush offers a longer, higher resistance path for, and materially reduces, harmful short circuiting or circulating currents set up between commutator bars, via the brush, during commutation. It will also be observed that the brush holder does not have to be altered to receive this brush.

In the modification shown in FIG, 3 the only difference is that two resilient bars 15 and 16 of rubber-like material have been substituted for the four plugs shown in FIG. 1. The two bars extend entirely across the brush half-sections 17 and 18 and are mounted in parallel recesses or slots 19 in one of those sections. The resilient bars press the brush sections against the opposite sides of the passage through the brush holder 24?.

Depending upon the needs of the specific application, the force with which the brush halves are held against the sides of the holder passage can be regulated by the length, cross section, number and degree of elasticity of the material used for spreading the brush sections apart.

According to the provisions of the patent statutes, we have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. An electric brush assembly comprising a pair of thin carbon brush half-sections disposed face to face and having inner and outer ends, said faces being substantially parallel and spaced apart, and a resilient bar disposed between said faces in engagement with both and connected to one of said sections, said bar extending along said faces transversely of said brush sections and being compressible by manual pressure applied to said brush sections to permit said assembly to be inserted in a brush holder passage in sliding engagement with two opposite sides thereof simultaneously.

2. An electric brush assembly comprising a pair of thin carbon brush half-sections disposed face to face and having inner and outer ends, said faces being substantially parallel and spaced apart, one of said faces being provided with a plurality of recesses spaced apart lengthwise of said sections, and a resilient member permanently mounted in each of said recesses and projecting therefrom into engagement with the other of said faces, said members being compressible by manual pressure ap plied to said brush sections to permit said assembly to be inserted in a brush holder passage in flat engagement with two opposite sides thereof simultaneously.

3. An electric brush assembly according to claim 2, in which said recesses are sockets spaced from the edges of said recessed face.

4. The combination with an electric brush holder having a passage therethrough provided with a pair of parallel opposite sides, of a brush assembly in said passage comprising a pair of thin carbon brush half-sections disposed face to face, said faces being substantially flat and parallel, and compressed resilient means confined entirely between said parallel faces and having a substantially flat surface engaging the said fiat face of one of said brush sections, and means connecting said resilient means to the other of said sections, said resilient means pressing said brush sections flat against said opposite sides of the brush holder passage.

5. An electric brush assembly comprising a pair of thin carbon brush half-sections disposed face to face and having inner and outer ends, said faces being substantially parallel and spaced apart, and a plurality of resilient members disposed between said faces in engagement with both and connected to one of said sections, a plurality of the resilient members being spaced lengthwise of the brush sections, and at least two of the resilient members being spaced transversely of the brush sections, said members being compressible by manual pressure applied to said brush sections to permit said assembly to be inserted in a brush holder passage in sliding engagement with two opposite sides thereof simultaneously.

6. An electric brush assembly comprising a pair of thin carbon brush half-sections disposed face to face and having inner and outer ends, said faces being substantially flat and parallel and spaced apart, and a resilient member disposed between said faces and connected to one of said sections, said member having a substantially fiat surface engaging said flat face of the other brush section, said member being compressible by manual pressure applied to said brush sections to permit said assembly to be inserted in a brush holder passage in sliding engagement with two opposite sides thereof simultaneously.

10/ 23 Great Britain.

5/60 France.

MILTON Q. HIRSHFIELD, Primary Examiner. 

1. AN ELECTRIC BRUSH ASSEMBLY COMPRISING A PAIR OF THIN CARBON BRUSH HALF-SECTIIONS DISPOSED FACE TO FACE AND HAVING INNER AND OUTER ENDS, SAID FACES BEING SUBSTANTIALLY PARALLEL AND SPACED APART, AND A RESILIENT BAR DISPOSED BETWEEN SAID FACES IN ENGAGEMENT WITH BOTH AND CONNECTED TO ONE OF SAID SECTIONS, SAID BAR EXTENDING ALONG SAID FACES TRANSVERSELY OF SAID BRUSH SECTIONS AND BEING COMPRESSIBLE BY MANUAL PRESSURE APPLIED TO SAID BRUSH SECTIONS TO PERMIT SAID ASSEMBLY TO BE INSERTED IN A BRUSH 